1. Field of the Invention
The present invention relates to a display device, and more particularly to a display device which includes a touch panel function.
2. Description of Related Art
As a display device which includes a coordinates inputting device, there has been known a display device which includes a touch panel.
The conventional touch panel is mainly of a resistance film type and adopts the structure which mounts the touch panel on the display panel. Accordingly, the conventional touch panel has drawbacks such that the visibility is deteriorated due to the increase of surface reflection, a mechanism which mounts the touch panel on the display becomes necessary, and a means which calibrates an output of the touch panel and a position of a display becomes necessary.
To overcome these drawbacks, a display device which incorporates a touch panel function in a display part is disclosed in, for example, following published or unpublished patent documents 1 and 2.
In the display device disclosed in patent document 1, the photo detection means is constituted of a photo sensor, a buffer TFT, an output selection TFT, and a reset TFT.
In the display device disclosed in patent document 1, initializing and reading of the photo sensor are performed in synchronism with a gate scanning signal supplied to a display part, and two-dimensional image data is outputted.
In the display device disclosed in patent document 2, a photo detection means is constituted of a photo sensor, a holding capacitance, an initializing means, and a latch means.
In the display device disclosed in patent document 2, light which is radiated to the photo sensor is binarized and is held by the latch means. The binarized signal is outputted from a signal line and is taken out as a two-dimensional image. The display device detects a change of image data when a finger approaches and is brought into contact with a display part and specifies a coordinate position.
Here, as prior art documents relevant to the present invention, following documents are named.    [Patent document 1] US2003076295A    [Patent document 2] EP1610210A